General Motors Co dismissed several high-ranking executives, including at least one vice president and two directors, for their roles in the still-unfolding drama over deadly ignition switches in older GM cars, people familiar with the matter told Reuters.

Michael Robinson, vice president for environmental, sustainability and regulatory affairs; Gay Kent, general director of vehicle safety and crashworthiness; and M. Carmen Benavides, recently reassigned as director of product investigations and safety regulations, were among 15 employees dismissed from GM, according to the sources.

They said others dismissed were William Kemp, a senior attorney responsible for engineering and safety issues; Lawrence Buonomo, head of product litigation in GM's legal department; and Jennifer Sevigny, an attorney who heads GM's field product assessment group.

GM Chief Executive Officer Mary Barra on Thursday said GM had dismissed 15 people, including engineers Ray DeGiorgio, designer of the defective switches linked to at least 13 deaths, and Gary Altman, chief engineer for the Chevrolet Cobalt and Saturn Ion, which used those switches.

Barra said "some were removed because of what we consider misconduct or incompetence. Others have been relieved because they simply didn't do enough: They didn't take responsibility (and) didn't act with any sense of urgency" to investigate causes of fatal crashes and inform senior management.

Barra declined to identify the 15 who have left and a GM spokesperson reiterated the company will not provide the names.

Attempts to contact Robinson were unsuccessful. Kent, Benavides, Kemp, Buonomo and Sevigny did not respond to telephone requests for comment.

Several of those dismissed worked on the GM legal staff under General Counsel Michael Millikin, who was one of several top GM executives cleared by investigator Anton Valukas, the chairman of GM's outside counsel Jenner & Block, in an internal probe that was released Thursday.

Prior to heading environmental and regulatory affairs, Robinson held several positions on the legal staff, including general counsel for GM North America.

As head of FPA, Sevigny often worked with the legal staff on lawsuits and legal claims.

Kent and Benavides were top safety officials who sat in on a number of internal meetings on the defective switches, according to the report.

Kemp sat on an important legal review committee that discussed lawsuits and was authorized to handle settlements up to $1.5 million.

The committee was chaired after March 2012 by lawyer Buonomo, the Valukas report said. Some members of the legal team thought the committee could serve to give GM early warnings of safety trends